So, another project I got cooking, is to convert a PG990 cassette, to 11-38, eventually maybe even 10-38/40.

So far I have made (ok, I had a guy that works for me do it) the CAD footwork, to do a 38 tooth cog for the rear, and a 36 tooth XX1 style chain ring. Before everybody starts looking funny at the 36T chain ring, keep in mind this is for a 24" bike, so 36T is not all that big.I also have taken a PG990 cassette apart, and plan to re-space it to 10 speed.I'm a little tied up right now, but the plan is to get this going ASAP, as this seems like a nice mod, and would fit my Zee drive train well.

I had him do an assembly, to check clearance of the teeth of the 36T, as that seems to be the big deal about the XX1 style rings.See attached image.

So, another project I got cooking, is to convert a PG990 cassette, to 11-38, eventually maybe even 10-38/40.

So far I have made (ok, I had a guy that works for me do it) the CAD footwork, to do a 38 tooth cog for the rear, and a 36 tooth XX1 style chain ring. Before everybody starts looking funny at the 36T chain ring, keep in mind this is for a 24" bike, so 36T is not all that big.I also have taken a PG990 cassette apart, and plan to re-space it to 10 speed.I'm a little tied up right now, but the plan is to get this going ASAP, as this seems like a nice mod, and would fit my Zee drive train well.

I had him do an assembly, to check clearance of the teeth of the 36T, as that seems to be the big deal about the XX1 style rings.See attached image.

Magura

I should steal your attached image since it has the right chain/sprocket dimensions for me to draft out crap. LOL

I should steal your attached image since it has the right chain/sprocket dimensions for me to draft out crap. LOL

-S

It would be easier to ask for what you exactly need, as my CAD guy has made all the formulas and what not.

Magura

Naah, got what I needed - everything else is easy with parametric programming (looks like your guy used solidworks)

-S

Indeed he does

He has pretty much the whole thing nailed by now, so whatever cog / chain ring, it takes him like 20 minutes to do. The shape of the teeth, are not the same all the tooth counts.That's why I had him make a chain, so it's possible to check tooth/chain clearance.

He has pretty much the whole thing nailed by now, so whatever cog / chain ring, it takes him like 20 minutes to do. The shape of the teeth, are not the same all the tooth counts.That's why I had him make a chain, so it's possible to check tooth/chain clearance.

Magura

...and if you model the chain correctly, you can use it in an assembly to check the ramping between cogs.

He has pretty much the whole thing nailed by now, so whatever cog / chain ring, it takes him like 20 minutes to do. The shape of the teeth, are not the same all the tooth counts.That's why I had him make a chain, so it's possible to check tooth/chain clearance.

Magura

...and if you model the chain correctly, you can use it in an assembly to check the ramping between cogs.

I got around to machining the PG990 cassette today.One thing that really surprised me, is how miserable the alignment and tolerances were on the original.It wasn't like 0.1mm here and there, but rather 0.25mm and the like.....holy crap! For a cassette that was considered their "top of the line", for a couple of years, I'd say that's minimally exceptional.

So, after getting the whole thing machined, it now runs true. I kinda look forward to see what that brings to the table, as that ought to offer fair tolerances on the derailleur adjustment, and perhaps better shifting.Just for kicks, I measured the alignment of a XTR cassette as well, it wasn't much better.

I decided against making it a 10 speed for now, as I figured I would have very limited use of neither a 10T nor a 38T, considering this goes on a very short chain stay 24" bike.That may change at some point though, as I did prepare a 38T add on.

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